Download Grade 9 Ohm`s law

Educator and Tagging Information
Learning Area:
Technology
Resource Name:
Technology
Assessment Exemplar Number:
TECHN9.106
Item/s:
1
Phase:
Senior Phase
Grade:
9
Tags:
Technology, systems and control, electrical systems, electronic circuits, output, input, Ohm’s law,
relationship, potential difference, current, resistance, electrical circuit, calculations, worksheet,
Formative Assessment
Assessment Type:
Formative
Assessment Form/s:
Worksheet
Copyright for included material:
N/A
Duration:
60 min
Learning Outcome(s) and Assessment Standard(s):
Learning Outcome 2: Technological Knowledge and Understanding
The learner will be able to understand and apply relevant technological knowledge ethically and
responsibly.
Assessment Standards
We know this when the learner
3 Systems and Control
3.2 Demonstrates knowledge and understanding of how simple electronic circuits and devices are
used to make an output respond to an input signal (e.g. resistors, light-emitting diodes, transistors,
push or magnetic switches, thermistors, light-dependent resistors).
Learning Space:
Assessment
Hyperlinks:
To be completed later.
Rating:
Number of questions for exemplar:
1
Easy questions:
Medium questions:
Difficult questions:
Question 1
Assessment Task
Ohm’s Law calculations
State Ohm’s Law.
[2 marks]
Explain the relationship between the potential difference, current and resistance in an electric
circuit.
[6 marks]
1.3 Use Ohm’s Law to calculate the following answers:
1.3.1 Calculate the resistance across the filament in a lamp with a current of 0,5 A when it is
connected to a supply of 220V.
[3 marks]
1.3.2 A lamp operates from a 220V supply. The resistance is 550Ω. Calculate the strength of the
current when it is lit.
[4 marks]
1.3.3 An electronic circuit needs a potential difference of 3,6V across a resistor when a current of
30mA is in it. Would the voltage be 3,6V if the resistor had a resistance of 96Ω? [5 marks]
[25 marks]
1.1
1.2
Suggested Solutions
Question
number
1.
Possible
marks
2 marks
6 marks
3 marks
Answers
1.1 Ohm's law says that in an electric circuit, the current passing through a
resistor between two points is related to the voltage difference between
the two points and inversely related to the electrical conductance between
the two points.
1.2 When the potential difference (voltage) increases, the current also
increases. All conductors of electricity have some resistance to current. If
the resistance in a circuit is increased, the current will be decreased.
1.3.1
V
=
220V
I
=
0.5A
R
=
x
V
I
220V
R
0.5 A
R
R= 440Ω
3
4 marks
1.3.2
V
=
I
R
220V
=
x
=
550Ω
V
R
220V
I
550
I
I= 0.4A
4
There are various ways of working out the answer. For example:
V
=
x
I
=
30mA (30mA ÷ 1000 = 0.03A)
R
=
96Ω
V=IxR
V = 0.03A x 96Ω
V = 2.88V
Answer: No, the voltage would be 2.88V and not 3.6V.
[25 marks]
Appendix of Assessment Tools
5 marks
1.3.3